This invention relates to an improvement in a device for reducing the quantity of NOx in the exhaust gas by recirculating the exhaust gas into the suction manifold in internal combustion engines.
The inventor of the present invention previously proposed an exhaust gas recirculating device for recirculating the exhaust gas (which shall be referred to as an EGR gas hereinafter) to a portion downstream of the throttle valve in the internal combustion engine. In this system, an EGR control valve and a variable throttle valve are provided in an EGR gas passage and the variable throttle valve is so arranged that its opening area varies in proportion to that of the throttle valve and that the pressure difference between the front and rear sides of the variable throttle valve is kept constant. However, the previous invention has the following disadvantages: the cost of special parts is high and the construction is complicated resulting in an increase in the assemblying processes. There have been increasing demands for an improved exhaust gas recirculating device that eliminates the above-mentioned drawbacks.